The present invention relates to a method and apparatus for measuring a concentration of vaporous hydrogen peroxide. More particularly, the present invention relates to a method and apparatus that measures the concentration of vaporous hydrogen peroxide continuously in an enclosure.
Hydrogen peroxide has wide commercial use. In the pharmaceutical industry, hydrogen peroxide is commonly used as a sterilant. For instance, hydrogen peroxide is used to sterilize enclosures and equipment of sterile operations. The equipment is located in a sealed enclosure known as an isolation barrier that protects the equipment from contamination. Periodically, the equipment and barrier are shut down for cleaning and sterilization. During sterilization, vaporous hydrogen peroxide is introduced into the barrier. A prior art technique to ensure proper sterilization includes placing biological indicators or challenges within the barrier prior to the sterilization cycle. After the sterilization cycle, which may proceed for one to three hours, the biological challenges are removed from the barrier. The biological challenges are then cultured to promote any growth. Culturing typically takes a minimum of eight hours.
Analysis of the biological challenges determines if any bacteria has survived the sterilization process. If all of the bacteria has been killed, the equipment and the barrier have been properly sterilized. Otherwise, if any bacteria has survived, the sterilization cycle must be repeated.
A significant disadvantage of using biological challenges is the inherent delay necessary to culture the biological challenges after they have been removed from the barrier. The ability of the biological challenges to survive in the presence of vaporous hydrogen peroxide is dependent upon the duration and concentration level of vaporous hydrogen peroxide during the sterilization cycle. If the concentration level of vaporous hydrogen peroxide was sufficiently high for a suitable time period, the biological challenges will not survive and sterilization would be complete.
Although it is well known that vaporous hydrogen peroxide in a sufficient concentration and time duration will kill bacteria and sterilize, a system or method to measure the concentration level of vaporous hydrogen peroxide has not been disclosed.